Recent research reveals that portable ultrasound can reveal plaques in peripheral arteries that may lead to heart attacks and strokes before symptoms arise, in both developed and developing country settings
A study of portable ultrasound carried out in the US, Canada and India has revealed the potential of this technology for detecting plaques in peripheral arteries that can lead to heart attacks and stroke before symptoms arise, in both developed and developing country settings, allowing preventive treatment in those affected. The study, published in Global Heart (the journal of the World Heart Federation), is by Dr Ram Bedi, Affiliate Assistant Professor, Department of Bioengineering, University of Washington, Seattle, WA, US, and Professor Jagat Narula, Editor-in-Chief of Global Heart and Icahn School of Medicine at Mount Sinai, New York, US, and colleagues.
Numerous studies have shown that it is possible to assess subclinical atherosclerotic cardiovascular disease (ASCVD) using ultrasound imaging. Since more portable and lower cost ultrasound devices are now entering the market, along with increased automation and functionality, it may be possible in future to routinely examine people with ultrasound to establish any ASCVD present before symptoms emerge, so that future disease can be prevented, for e.g. using medication. In this study, ASCVD was determined using ultrasound of both the carotid arteries (those in the neck) and the ileofemoral arteries (entering the top of the leg). The findings were summarised in an index called the Fuster-Narula (FUN) Score.
Data were gathered from four cohorts, two Indian and two North American. In India, screening with automated ultrasound imaging was conducted over eight days in 941 relatively young (mean age 44 years, 34 per cent female) asymptomatic volunteers recruited from the semiurban town of Sirsa (Haryana) and urban city of Jaipur (Rajasthan) in northern India. The cohort from Sirsa was recruited because all participants had already undergone aggressive lifestyle changes (smoking cessation, no alcohol, vegetarian diet, physically active lifestyles, daily meditation).
To compare the imaging findings with traditional risk factors, two cohorts (481 persons) were recruited from primary care clinics in North America (one in Richmond, Texas, US, the other in Toronto, Canada). Apart from the same ultrasound examinations given in the Indian cohort, comprehensive ASCVD risk factor data was gathered from the participants. All of them were self-referred asymptomatic individuals (mean age 60 years, 39 per cent female). Data collected included cholesterol levels, blood pressure, glucose level, weight, height, smoking and family history. These people were attending clinics for routine health check-ups in most cases. Effectiveness of established ASCVD prevention guidelines was then compared to results from direct imaging.
In India, ultrasound revealed plaques in at least one artery in almost a quarter (24 per cent) of those examined; 107 (11 per cent) had plaques in only the carotids, 70 (seven per cent) in both the carotids and iliofemoral arteries, and 47 (five per cent) had plaques in only the iliofemoral arteries. If just the carotids had been examined, 177 (19 per cent) of the asymptomatic subjects would have been identified with plaques; by adding the iliofemoral examination, 47 additional individuals (five per cent of the total) were identified with plaque. Older age and male sex were associated with the presence of plaque both in urban and semiurban populations (the much higher levels of smoking in men could account for their higher risk).
Data from the American and Canadian clinics showed that 203 subjects (42 per cent) had carotid plaque; 166 of these (82 per cent of those with plaque) would not have qualified for lipid-lowering therapy such as statins under widely used guidelines known as ATP III (Third Report of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults [Adult Treatment Panel]) guidelines. Using the recently published more stringent ATP IV guidelines, 67 people (one third of those with plaque and 14 per cent of the total US/Canadian cohort) individuals with carotid plaque would also have failed to qualify for treatment.
In addition, the study revealed 34 people in the US/ Canada setting who qualified for treatment under ATP III but did not have any plaques, and this number increased to 81 under ATP IV (if receiving treatment such as statins, these people could be said to be overtreated, since no plaques were evident).
The authors say, “Our study shows that automation in ultrasound imaging technology allows even non-expert users to rapidly evaluate the presence of subclinical atherosclerosis in a large population. Detection of sub-clinical atherosclerosis is further enhanced by inclusion of the iliofemoral artery examination.” They add, “It seems that plaque information from ultrasound images may serve as a guide for initiating medical intervention regardless of the availability or knowledge of traditional risk factors. Our results further suggest that not only in low- and middle-income countries, but even in the developed nations, ultrasound images may help refine strategies for medical intervention. It might however still be too contentious to suggest that risk factors–positive and imaging-negative asymptomatic subjects may be spared from medical intervention. Conversely, arguments against initiating medical intervention on risk factors–negative and imaging-positive asymptomatic subjects become harder to justify.”
In a linked comment, Dr Tasneem Z Naqvi, Professor of Medicine , Mayo College of Medicine and Division of Cardiology, Scottsdale, Arizona, US, adds, “This study shows that the assessment of subclinical atherosclerosis by a portable, user-friendly bedside tool is feasible in large populations and the technique of carotid ultrasound imaging and IMT assessment could be adopted by novices after an eight-hour crash course.” She concludes that the study shows that vascular ultrasound imaging technology is ripe and the previously existing barriers like poor resolution, cumbersome protocols, need for off line processing and need for expert performer no longer exist. However, she says that the study does not address whether this imaging-based approach would save more lives than the risk-based approach. “We need to ponder if treating nearly 50 per cent of the adults with statins with a risk scoring algorithm is more appropriate versus treating only those who have subclinical atherosclerosis based on comprehensive and readily available, cheap and simple screening method,” she says. The study makes a compelling argument in favour of imaging for screening, she states.